firebase cloud messages coming without any sounds

Question

I am working on a Cloud messaging application, and I am using the Firebase cloud messages, by this code

public class NotificationHelper {

    public static void displayNotification(Context context, String title, String body) {
        Uri alertSound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

        NotificationCompat.Builder  mBuilder =
                new NotificationCompat.Builder(context, MainActivity.CHANNEL_ID)
                        .setSmallIcon(R.drawable.ic_gift )
                        .setContentTitle(title)
                        .setContentText(body)
                        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                        .setSound(alertSound);

        NotificationManagerCompat notificationManagerCompat =  NotificationManagerCompat.from(context);
        notificationManagerCompat.notify(1, mBuilder.build());
    }
}

and this is the service.

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        if (remoteMessage.getNotification() != null) {
            String title = remoteMessage.getNotification().getTitle();
            String text = remoteMessage.getNotification().getBody();
            NotificationHelper.displayNotification(getApplicationContext(), title, text);
        }
    }
}

and this is the manifest XML code

<service
    android:name=".MyFirebaseMessagingService">
    <intent-filter>
        <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
    </intent-filter>
</service>

and the messages coming but without any sounds, I do not know what it the wrong thing in my code, please anyone can help me